1. Field of the Invention
The present invention relates to a patterned polygon rendering apparatus, in the field of computer graphics, which pastes a pattern to a polygon of arbitrary shape, to thus perform painting.
2. Description of the Related Art
In recent years, a polygon having a pattern (hereinafter referred to as a “patterned polygon”) has been extensively used for representing a green space or the sea, in a map display of a car navigation system. A conventionally-proposed method for rendering a patterned polygon is to divide a polygon into smaller polygons and to paste a texture, which is a pattern, to each of the thus-divided smaller polygons (see, e.g., JP-A-6-301792 (pp. 3 to 5, FIG. 1)).
However, the related-art method suffers a problem of heavy processing load for dividing a polygon into smaller polygons or computing reference coordinates of patterns assigned to the divided smaller polygons, or a problem of an increase in the number of memory write operations involving shorter transfer lengths, because the graphic divided into the smaller polygons becomes smaller in terms of the number of rendering pixels, thereby degrading rendering performance under influence of latency of memory access.